This invention relates to spirit levels, and more particularly, to means for installing and retaining liquid-containing leveling vials, and to additional means for retaining and sealing transparent sight plates used to protect the leveling vials from dirt or other foreign matter.
The spirit level includes a frame having one or more holes into which is installed a vial holder having a central opening therethrough. Tubular leveling vials extend across the central opening and pass into vial receiving ports in the vial holder. In a preferred embodiment of the level, the vials extend through the ports and terminate in recesses which open into the vial holder from its radially outer sides. These recesses are filled with cement or the like which fixes the vials in the vial holder, and concurrently attaches the vial holder to the surface of the frame forming the hole.
Previous spirit levels utilized a vial holder with no outer recesses, which required reliefs to be cut into the frame radially outward from the surface of the frame forming the hole. The ends of the vials extended into such reliefs and were cemented in place. Positioning the vials and the cementing operation are much simpler with the new configuration. In addition, the cutting of the holes in the frame is greatly simplified, and the vial holder can be easily injection molded from a plastic or similar material.
A transparent sight plate is used to cover each exposed end of the central opening through the vial holder by extension substantially across the hole in the frame. Each plate is held in place by an endless gasket having a central opening therethrough. In a preferred embodiment, a unique resilient gasket is utilized and has a first monoplanar surface which flatly contacts the plate and has a lip angling out of the monoplanar surface and sealingly deflected against the plate. The preferred gasket also includes a second peripheral surface which contacts the defining surface of the frame opening. The preferred gasket also includes a radially outward flange which extends into a radial groove around the frame hole, and the flange and grooves are dimensioned such that the monoplanar surface of the gasket is maintained in flat contact with the sight plate. The flange may be cemented into the groove to fix the gasket in position and to provide a continuous seal between the gasket, frame and sight plate.
Previous spirit levels used putty to retain the sight plate and to seal around it. Applying the putty properly was a slow and tedious process, and, after a period of time, the putty would age and crack thereby breaking the seal around the sight plate. The only method of repairing such a cracked putty seal or of replacing a broken sight plate was to return the level to the factory. The present invention eliminates these problems. In contrast to the putty, the gasket is easily and quickly installed and has a consistent, uniform appearance. A suitable material for the gasket is chosen so that it is not as prone to age or crack, thereby giving it a much improved effective service life as compared to putty. The gasket and cement materials are compatibly selected so that the gasket can be removed for simple field repair of a damaged gasket or plate.
From the foregoing description of the present invention, it will be apparent that an important object of the invention is to provide an improved vial holder structure for use in a spirit level device, which vial holder structure can be more easily located within the spirit level frame, and which can be more easily replaced if the vial holder or the vials held thereby become damaged.
A further object of the invention is to provide an improved structure for retaining protective sight glasses in position on opposite sides of liquid-containing spirit level vials in a spirit level structure.
A further object of the invention is to obviate the necessity to recaulk spirit level sight glasses which have become loose due to cracking and loss of integrity of a caulk sealant used to retain the spirit level sight glasses in the spirit level frame.
Additional objects and advantages of the invention will become apparent from the following detailed description of a preferred embodiment of the invention when the same is read in conjunction with the accompanying drawings which illustrate such embodiment.